1. Technical Field
The present invention relates to arrangement of various light-emitting elements, such as organic light-emitting diodes (hereinafter, referred to as “OLEDs”).
2. Related Art
A light-emitting device having a plurality of light-emitting elements arranged on a substrate is used, for example, as an exposure device (optical head) for exposing an image bearing member in an electrophotographic image forming apparatus. JP-A-8-108568 discloses a light-emitting device that has a plurality of light-emitting elements arranged in two rows in a zigzag manner. That is, two rows of element groups each having a plurality of light-emitting elements arranged in a main scanning direction are arranged to be spaced at an interval in a sub-scanning direction. The light-emitting elements in the element group of the first row and the light-emitting elements in the element group of the second row are provided at different positions in the main scanning direction.
To achieve high-definition for an image (latent image) to be formed on the image bearing member by the light-emitting device, the number of rows of element groups may be increased. However, the increase in the number of rows of element groups leads to an increase in the dimension of a region in the sub-scanning direction (hereinafter, referred to as “element forming region” where each light-emitting element is to be formed. The increase in the dimension of the element forming region in the sub-scanning direction results in deterioration of image formation performance of the image bearing member or an increase in the size of the light-emitting device.